title: Brain creatine kinase with aging in F-344 rats: analysis by saturation transfer magnetic resonance spectroscopy.
abstract: We measured in vivo forward flux of the creatine kinase reaction in rat forebrain in young (Y: 6 month, n = 13), mid-aged (M: 12 month, n = 7) and aged (O: 27 month, n = 10) animals using 31P magnetic resonance saturation transfer. Forward flux was reduced in the aged rats (Y: 0.42 +/- 0.08; M: 0.41 +/- 0.10; O: 0.31 +/- 0.03 s(-1) +/- SD; p = 0.008 O vs. Y). In vitro studies in a subset of the same rats showed a parallel decline in CK activity (Y: 2.16 +/- 0.40; M: 2.17 +/- 0.25; O: 1.56 +/- 0.06 IU +/- S.D.; p = 0.002 O vs. Y). The in vivo spectroscopic and in vitro biochemical measures were significantly correlated. Reduced creatine kinase activity could account for the observed decreased forward flux in aging brain. Intracellular pH, phosphocreatine/inorganic phosphate ratio, and phospocreatine/gamma-adenosine triphosphate ratio did not differ between groups. Forward flux may represent a better measure of brain energy function than relative phosphocreatine or adenosine triphosphate levels observable in vivo.
authors.affiliation: Magnetic Resonance Imaging and Spectroscopy Center, Department of Neurology, University of Kentucky College of Medicine, Lexington 40536, USA. csmith@mri.uky.edu
authors.forename: C D
authors.initials: CD
authors.lastname: Smith
authors.forename: W
authors.initials: W
authors.lastname: Landrum
authors.forename: J M
authors.initials: JM
authors.lastname: Carney
authors.forename: P W
authors.initials: PW
authors.lastname: Landfield
authors.forename: M J
authors.initials: MJ
authors.lastname: Avison
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D001921:Brain / Q000201:enzymology* / Q000254:growth & development*; D003402:Creatine Kinase / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D019906:Nuclear Magnetic Resonance, Biomolecular; D051381:Rats; D011916:Rats, Inbred F344
chemical_list: D003402:Creatine Kinase